1. Field of the Invention
The present invention relates to the use of a linked compound as a fiber lubricant yielding a very low level of residue when oxidized at high temperatures. More particularly, a compound linked with formal, acetal, ketal and carbonate is useful as a fiber lubricant when applied to a fiber in an amount of from 0.05 weight percent to 5 weight percent, based on the weight of the fiber lubricant, because the lubricant provides less than 10 weight percent loss at a temperature of less than 230.degree. C. and a residue of less than two weight percent, based on the weight of fiber lubricant, after oxidation at a temperature of about 240.degree. C. for 24 hours.
2. Description of the Prior Art
A fiber lubricant formulation consists of a base material such as mineral oil, alkyl esters of fatty acids or vegetable oils, emulsifiers that allow the lubricant to be applied from a water solution, antistatic agents, antioxidants, bacteriocides, friction modifiers or buffering agents.
A fiber lubricant is critical to the conversion of nylon or polyester fiber into useful yarn for textile manufacturing. The fiber lubricant has several functions. One function is to control friction. The fiber lubricant may protect the newly spun fiber from fusion or breakage by controlling the yarn to metal friction at frictional contact points between the yarn and machine guides, rollers, draw plates, heater plate and texturing false twist spindles or friction discs. Another function is to protect the fiber from heat generated at a heater temperature by heater plates or from heat at the frictional contact points. The lubricant also functions to provide for yarn cohesion giving strength to the yarn by holding the yarn bundled together and by allowing the yarn to build up an acceptable package at the end of processing. Static electricity that is formed as the yarn rapidly moves through the processing equipment would also be controlled. The lubricant must also protect machine surfaces from wear.
Synthetic fibers are drawn and textured or bulked to yield optimum physical properties of strength, increased covering, pleasing hand, and greater warmth. During both texturing and bulking, the yarn is exposed to high temperatures such as by passing the fibers through a heating zone. In the heating zone, the fibers are heated to a fiber temperature by a heater plate at a heater plate temperature.
The fiber temperature is within a fixed temperature range within which the fiber will remember an orientation or other imparted characteristic. The fiber lubricant must show acceptable thermal stability in air and should evaporate very little or have low volatility at the fiber temperature.
The heater plate temperature has been increased by the manufacturers in recent years in order to provide faster throughput. Since the fiber temperature is a function of the heater plate temperature and the length of the time in the heating zone, as the speed of the fiber throughput increases, the fiber temperature may be maintained by increasing the heater plate temperature. Increased fiber speed places increased stress on the lubricant to protect the fiber. Increased heater plate temperature places increased demands on the fiber lubricant degradation. It has become increasingly more important that fiber lubricants degrade at high temperatures, such as at the heater plate temperature, in a controlled manner without leaving a residue. The fiber lubricant should evaporate very little at the fiber temperature, but that fiber lubricant which does evaporate should, upon approaching the heater plate temperature, degrade to volatile products leaving a very small residue.
Compounds containing acetal linkages have been disclosed in the prior art as evidenced by U.S. Pat. No. 2,786,081 which discloses polymeric condensation products of polyalkylene glycols and aldehydes. U.S. Pat. No. 4,189,609 makes a very general suggestion to use formal-containing products in textile applications, however, there is no suggestion that formal-containing products would have use as a fiber finish component because of their unique thermal properties.